Giant magnetoresistive element

ABSTRACT

A giant magnetoresistive (GMR) element includes a first antiferromagnetic layer, a pinned magnetic layer in which the magnetization direction is pinned by the first antiferromagnetic layer, a nonmagnetic material layer, a free magnetic layer in which that the magnetization direction of a central portion changes with an external magnetic field, a nonmagnetic layer, ferromagnetic layers formed on both side portions of the nonmagnetic layer, and second antiferromagnetic layers for aligning the magnetization direction of each ferromagnetic layer in a direction perpendicular to the magnetization direction of the pinned magnetic layer. In the GMR element, the magnetization direction of the free magnetic layer and the ferromagnetic layers are antiparallel to each other through the nonmagnetic layer, and at least the free magnetic layer, the nonmagnetic layers and the ferromagnetic layers have continuous surfaces α at both end surfaces in the track width direction. Furthermore, first electrode layers are provided in contact with the continuous surfaces α, and second electrode layers are provided on the first electrode layers and the second antiferromagnetic layers.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a giant magnetoresistive elementused for a hard disk device, a magnetic sensor, and the like, and amethod of manufacturing the same.

[0003] 2. Description of the Related Art

[0004] In a giant magnetoresistive element (GMR) used for a hard diskdevice, a magnetic sensor, and the like, an improvement in outputsensitivity and narrowing of a track have recently been advanced withincreases in the recording density.

[0005] In order to improve the output sensitivity, a magnetic moment(areal moment) per unit area of a free magnetic layer is conventionallydecreased by thinning the free magnetic layer to facilitatemagnetization rotation of the magnetic moment. However, with the thinfree magnetic layer, Barkhausen noise, thermal fluctuation noise, andthe like are increased to cause the problem that a SN ratio cannot beincreased even by increasing the output sensitivity. Also, a hard biassystem using a permanent magnet film is conventionally used for the freemagnetic layer. However, in the hard bias system, magnetization isstrongly fixed at both side ends of the free magnetic layer adjacent tothe permanent magnet film to produce dead zones, thereby causing theprobability that the entire track region becomes a dead zone whennarrowing of the track is advanced. Therefore, it is predicted that thehard bias system using the permanent magnet film is difficult to complywith a higher recording density.

[0006] Therefore, an exchange bias system has recently been proposed asthe bias system for the free magnetic layer. As is generally known, aGMR element has a structure in which a first antiferromagnetic layer, apinned magnetic layer, a nonmagnetic material layer and a free magneticlayer are laminated in turn. In the use of the exchange bias system,second antiferromagnetic layers and electrode layers are further formedon both sides of the free magnetic layer so that the track width of theGMR element is controlled by the distance between the secondantiferromagnetic layers in the track width direction. In the use of theexchange bias system, no dead zone occurs, and thus output sensitivitycan be possibly secured even with advances in track narrowing.

[0007] However, in the free magnetic layer, an exchange interaction actsbetween adjacent spins to orient the adjacent spins in paralleldirections, and thus a distance corresponding to the strength of theexchange interaction between the adjacent spins is required for rotatingthe spins by an angle according to the strength of an external magneticfield. The strength of the exchange interaction can be represented by anexchange stiffness constant (exchange interaction constant). As theexchange stiffness constant increases, a spin direction cannot berapidly changed to increase a distance required for spin rotation. Whenthe distance required for spin rotation is increased, magnetizationfixing at the ends of the track width region is strongly transmitted tothe central portion, thereby decreasing the output sensitivity. Thistendency becomes remarkable as the track width dimension decreases, andthus the output sensitivity cannot be easily secured even by using theexchange bias system. As a possible countermeasure against this, thefree magnetic layer is made of a material having a small exchangestiffness constant. However, the use of the material having a smallexchange stiffness constant undesirably decreases the Curie temperature.Also, the selection of the material has a limitation.

[0008] Furthermore, the use of the exchange bias system has thefollowing problem.

[0009] Since a sensing current flows in the free magnetic layer throughthe antiferromagnetic layers having extremely higher resistivity thanthat of the electrode layers, the element resistance is increased. Whenthe element resistance is increased, impedance is also increased toeasily produce high-frequency noise, thereby failing to increase the SNratio even with the improved output sensitivity.

SUMMARY OF THE INVENTION

[0010] The present invention has been achieved in consideration of theproblem of the use of a conventional exchange bias system, and it is anobject of the present invention to provide a giant magnetoresistiveelement capable of securing high output sensitivity even with advancesin track narrowing, and a method of manufacturing the same. Anotherobject of the present invention is to provide a giant magnetoresistiveelement capable of decreasing the element resistance, and a method ofmanufacturing the same.

[0011] The present invention has been achieved with attention to thepoint that output sensitivity can be improved by using a demagnetizingfield produced in a free magnetic layer in the track width directionthereof, and the point that the element resistance can be decreased bysupplying a sensing current without passing through an antiferromagneticlayer.

[0012] A giant magnetoresistive element of the present inventioncomprises a first antiferromagnetic layer, a pinned magnetic layerformed on the first antiferromagnetic layer so that the magnetizationdirection is pinned by an exchange coupling magnetic field with thefirst antiferromagnetic layer, a nonmagnetic material layer formed onthe pinned magnetic layer, a free magnetic layer formed on thenonmagnetic material layer so that the magnetization direction of acentral portion changes with an external magnetic field, nonmagneticlayers formed on both side portions of the free magnetic layer in thetrack width direction, ferromagnetic layers formed on the respectivenonmagnetic layers, and second antiferromagnetic layers formed on therespective ferromagnetic layers to align the magnetization direction ofeach ferromagnetic layer in a direction perpendicular to themagnetization direction of the pinned magnetic layer, wherein at leastthe free magnetic layer, the nonmagnetic layers and the ferromagneticlayers have continuous end surfaces at both sides in the track widthdirection.

[0013] In the above-described construction, magnetostatic couplingoccurs between the free magnetic layer and the ferromagnetic layers atboth end surfaces thereof, and thus a demagnetizing field applied in thefree magnetic layer in the track width direction thereof is weakened bythe magnetostatic coupling. Namely, even if the demagnetizing field isincreased by narrowing the track, disturbance of magnetization of eachof the free magnetic layer and the ferromagnetic layers can besufficiently suppressed to secure high stability of a reproductionwaveform. Also, the magnetization directions of both side portions ofthe free magnetic layer and the ferromagnetic layers are strongly pinnedby the second antiferromagnetic layers. Therefore, even if thedemagnetizing field is increased by narrowing the track, there is noprobability of side reading.

[0014] The ratio FW/FL of the dimension FW of the free magnetic layer inthe track width direction to the dimension FL of the ferromagneticlayers in the track width direction is preferably 1.1 to 2.0. With aFW/FL ratio within this range, magnetization of a track width region (acentral portion of the free magnetic layer) easily rotates with anexternal magnetic field to improve output sensitivity. The dimension FLof the free magnetic layers in the track width direction is a totaldimension FL1+FL2 of the dimensions of FL1 and FL2 of the respectiveferromagnetic layers in the track width direction.

[0015] The above-described giant magnetoresistive element preferablyfurther comprises electrode layers formed in contact with the uppersurfaces of the respective second antiferromagnetic layers and contactwith both end surfaces of the layers ranging from the respectiveantiferromagnetic layers to the pinned magnetic layer in the track widthdirection. Each of the electrode layers comprises a first electrodelayer formed in contact with the end surfaces of the layers ranging fromthe pinned magnetic layer to each second antiferromagnetic layer at eachside in the track width direction, and a second electrode layer formedon the first electrode layer and each second antiferromagnetic layer. Inthis construction, a sensing current can be supplied without passingthrough the second antiferromagnetic layers having extremely higherresistivity than that of a conductive material for forming the electrodelayers. Therefore, the element resistance can be sufficiently suppressedto suppress the occurrence of high-frequency noise, thereby improvingthe SN ratio.

[0016] Each of the second antiferromagnetic layers may comprise a lowerantiferromagnetic layer laminated on each ferromagnetic layer, and anupper antiferromagnetic layer. In this case, the lower antiferromagneticlayers are preferably 20 Å to 50 Å in thickness. With the lowerantiferromagnetic layers each having a thickness in this range, thelower antiferromagnetic layers do not assume antiferromagneticproperties in a stage in which only the lower antiferromagnetic layersare formed (the upper antiferromagnetic layers are not formed).Therefore, even in a first heat treatment for pinning the magnetizationdirection of the pinned magnetic layer, no or a weak exchange couplingmagnetic field occurs between each of the lower antiferromagnetic layersand the ferromagnetic layer. On the other hand, in a stage in which theupper antiferromagnetic layers are formed on the lower antiferromagneticlayers, a heat treatment produces great exchange coupling magneticfields between the ferromagnetic layers and the lower antiferromagneticlayers. Therefore, the total thickness of each lower antiferromagneticlayer and upper antiferromagnetic layer is preferably 80 Å to 300 Å.

[0017] A nonmagnetic protective layer may be interposed between eachlower antiferromagnetic layer and upper antiferromagnetic layer, or aconstituent element of the nonmagnetic protective layer may be mixed inthe lower antiferromagnetic or upper antiferromagnetic layers. However,the thickness of each nonmagnetic protective layer is preferably 3 Å orless so that the lower antiferromagnetic and upper antiferromagneticlayers can function as an antiferromagnetic layer as a unit. Theconstituent element of the nonmagnetic protective layers is preferablyat least one of Ru, Rh, Pd, Ir, Os, Re, Cr, Cu, Pt, and Au. Thenonmagnetic protective layers function as antioxidation films forprotecting the surfaces of the lower antiferromagnetic layers fromoxidation in the manufacturing process.

[0018] In a first aspect of the present invention, a method ofmanufacturing a giant magnetoresistive element comprises (a) a step oflaminating a first antiferromagnetic layer, a pinned magnetic layer, anonmagnetic material layer, a free magnetic layer and a nonmagneticlayer in order on a substrate; (b) a step of performing a first heattreatment to pin the magnetization direction of the pinned magneticlayer by an exchange coupling magnetic field produced between the firstantiferromagnetic layer and the pinned magnetic layer; (c) a step ofcleaning the surface of the nonmagnetic layer by low-energy ion milling;(d) a step of laminating a ferromagnetic layer and a secondantiferromagnetic layer in order on the nonmagnetic layer; (e) a step offorming a resist layer on a region of the second antiferromagnetic layercorresponding to a track width region; (f) a step of removing exposedportions of at least the second antiferromagnetic layer, theferromagnetic layer, the nonmagnetic layer and the free magnetic layer,which are partially exposed from both sidesof the resist layer in thetrack width direction; (g) a step of removing the resist layer andforming an electrode layer on regions of the second antiferromagneticlayer out of the track width region; (h) a step of partially removingthe second antiferromagnetic layer, the ferromagnetic layer and thenonmagnetic layer within the track width region by etching using theelectrode layer as a mask; and (i) a step of performing a second heattreatment to pin the magnetic direction of the ferromagnetic layer in adirection perpendicular to the magnetization direction of the pinnedmagnetic layer by exchange coupling produced between the secondantiferromagnetic layer and the ferromagnetic layer, wherein in thesteps (a) and (d), the free magnetic layer and the ferromagnetic layerare formed so that the magnetic moment per unit area of the freemagnetic layer is larger than that of the ferromagnetic layer, in thestep (c), the nonmagnetic layer is removed by the low-energy ion millingto a thickness with which RKKY coupling energy produced between the freemagnetic layer and the ferromagnetic layer is a first peak or secondpeak value for antiparallel alignment, and in the step (f), the layersranging from the second antiferromagnetic layer to the free magneticlayer are left to have continuous surfaces at both end surfaces in thetrack width direction.

[0019] In a second aspect of the present invention, a method ofmanufacturing a giant magnetoresistive element comprises (m) a step oflaminating a first antiferromagnetic layer, a pinned magnetic layer, anonmagnetic material layer, a free magnetic layer and a nonmagneticlayer, a ferromagnetic layer, a lower antiferromagnetic layer and anonmagnetic protective layer in order on a substrate; (n) a step ofperforming a first heat treatment to pin the magnetization direction ofthe pinned magnetic layer by an exchange coupling magnetic fieldproduced between the first antiferromagnetic layer and the pinnedmagnetic layer; (o) a step of cleaning the surface of the nonmagneticprotective layer by low-energy ion milling; (p) a step of laminating anupper antiferromagnetic layer on the nonmagnetic protective layer; (r) astep of forming a resist layer on a region of the upperantiferromagnetic layer corresponding to a track width region; (s) astep of removing exposed portions of at least the upperantiferromagnetic layer, the nonmagnetic protective layer, the lowerantiferromagnetic layer, the ferromagnetic layer, the nonmagnetic layerand the free magnetic layer, which are partially exposed from both sidesof the resist layer in the track width direction; (t) a step of removingthe resist layer and forming an electrode layer on regions of the upperantiferromagnetic layer out of the track width region; (u) a step ofpartially removing the upper antiferromagnetic layer, the nonmagneticprotective layer, the lower antiferromagnetic layer, the ferromagneticlayer and the nonmagnetic layer within the track width region by etchingusing the electrode layer as a mask; and (v) a step of performing asecond heat treatment to pin the magnetization direction of theferromagnetic layer in a direction perpendicular to the magnetizationdirection of the pinned magnetic layer by exchange coupling producedbetween the lower antiferromagnetic layer and the ferromagnetic layer,wherein in the step (m), the free magnetic layer and the ferromagneticlayer are formed so that the magnetic moment per unit area of the freemagnetic layer is larger than that of the ferromagnetic layer, and thenonmagnetic layer is formed to a thickness with which RKKY couplingenergy produced between the free magnetic layer and the ferromagneticlayer is a first peak or second peak value for antiparallel alignment,and in the step (s), the layers ranging from the upper antiferromagneticlayer to the free magnetic layer are left to have continuous surfaces atboth end surfaces in the track width direction.

[0020] The ratio FW/FL of the dimension FW of the free magnetic layer inthe track width direction to the dimension FL of the ferromagneticlayers in the same direction is preferably 1.1 to 2.0.

[0021] In each of the aspects of the present invention, the electrodelayer may comprise a first electrode layer in contact with the endsurfaces of the layers from the second antiferromagnetic layer to thepinned magnetic layer at each side in the track width direction, and asecond electrode layer disposed on the first electrode layer and thesecond antiferromagnetic layer. Namely, in the first aspect, in place ofthe step (g), a step (j) of forming a first electrode layer in contactwith the end surfaces of at least the layers ranging from the secondantiferromagnetic layer to the pinned magnetic layer at each side in thetrack width direction, (k) a step of removing the resist layer, (l) astep of forming a second electrode layer on the first electrode layerand the second antiferromagnetic layer outside the track width regionmay be performed. In the second aspect, in place of the step (t), a step(w) of forming a first electrode layer in contact with the end surfacesof at least the layers ranging from the upper antiferromagnetic layer tothe pinned magnetic layer at each side in the track width direction, (x)a step of removing the resist layer, (y) a step of forming a secondelectrode layer on the first electrode layer and the upperantiferromagnetic layer outside the track width region may be performed.

[0022] The lower antiferromagnetic layer is preferably deposited to athickness of 20 Å to 50 Å. With a thickness within this range, the lowerantiferromagnetic layer do not assume the antiferromagnetic propertiesin the stage in which only the lower antiferromagnetic layer is formed(the upper antiferromagnetic layer is not formed). Therefore, even in afirst heat treatment for pinning the magnetization direction of thepinned magnetic layer, no or a weak exchange coupling magnetic fieldoccurs between the lower antiferromagnetic layer and the ferromagneticlayer. On the other hand, in the stage in which the upperantiferromagnetic layer is formed on the lower antiferromagnetic layer,a heat treatment produces a great exchange coupling magnetic fieldbetween the ferromagnetic layer and the lower antiferromagnetic layer.Therefore, the total thickness of the lower antiferromagnetic layer andupper antiferromagnetic layer is preferably 80 Å to 300 Å.

[0023] The nonmagnetic protective layer is preferably deposited to athickness of 3 Å to 10 Å so that oxidation of the lowerantiferromagnetic layer can be prevent, and the nonmagnetic protectivelayer can easily be removed. The nonmagnetic protective layer ispreferably controlled to a thickness of 3 Å or less by low-energy ionmilling. In this case, the lower and upper antiferromagnetic layers arecoupled with each other through the nonmagnetic protective layer tofunction as an antiferromagnetic layer as a unit.

[0024] Each of the free magnetic layer and the ferromagnetic layer maycomprise any one of a NiFe alloy, Co, a CoFe alloy, a CoNi alloy, and aCoFeNi alloy. The free magnetic layer and ferromagnetic layer arepreferably made of the same magnetic material. When the free magneticlayer and ferromagnetic layer are made of the same magnetic material,the thickness of the ferromagnetic layer is made smaller than that ofthe free magnetic layer so that the magnetic moment per unit area of thefree magnetic layer is larger than that of the ferromagnetic layer. Wheneach of the free magnetic layer and ferromagnetic layer comprises asingle layer, at least one of the free magnetic layer and ferromagneticlayer preferably comprises a CoFeNi alloy. Furthermore, when each of thefree magnetic layer and ferromagnetic layer comprises a plurality oflayers, the free magnetic layer preferably comprises a laminate of aNiFe alloy layer and a CoFe alloy layer, and the ferromagnetic layerpreferably comprises a laminate of a CoFe alloy layer and a NiFe alloylayer.

[0025] The nonmagnetic layer is preferably composed of at least one ofRu, Rh, Pd, Ir, Os, Re, Cr, Cu, Pt. and Au, and particularly thenonmagnetic layer is preferably composed of Ru or Cu.

[0026] The first antiferromagnetic and/or second antiferromagnetic layerpreferably comprises a PtMn alloy, a X—Mn (wherein X is at least oneelement of Pd, Ir, Rh, Ru, Os, Ni, and Fe) alloy, or a Pt—Mn—X′ (whereinX′ is at least one element of Pd, Ir, Rh, Ru, Au, Ag, Os, Cr, Ni, Ar,Ne, Xe, and Kr) alloy. With the first antiferromagnetic layer and/orsecond antiferromagnetic comprising any one of these alloys, a largeexchange coupling magnetic field can be produced between the firstantiferromagnetic layer and the pinned magnetic layer and/or the secondantiferromagnetic layer and the ferromagnetic layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a partial sectional view showing the structure of agiant magnetoresistive element (GMR element) according to a firstembodiment of the present invention, as viewed from a surface facing arecording medium;

[0028]FIG. 2 is a drawing showing a step of a method of manufacturingthe GMR element shown in FIG. 1;

[0029]FIG. 3 is a drawing showing a step after the step shown in FIG. 2;

[0030]FIG. 4 is a drawing showing a step after the step shown in FIG. 3;

[0031]FIG. 5 is a drawing showing a step after the step shown in FIG. 4;

[0032]FIG. 6 is a drawing showing a step after the step shown in FIG. 5;

[0033]FIG. 7 is a drawing showing a step after the step shown in FIG. 6;

[0034]FIG. 8 is a drawing showing a step after the step shown in FIG. 7;

[0035]FIG. 9 is a partial sectional view showing the structure of a GMRelement according to a second embodiment of the present invention, asviewed from a surface facing a recording medium;

[0036]FIG. 10 is a drawing showing a step of a method of manufacturingthe GMR element shown in FIG. 9;

[0037]FIG. 11 is a drawing showing a step after the step shown in FIG.10;

[0038]FIG. 12 is a drawing showing a step after the step shown in FIG.11;

[0039]FIG. 13 is a drawing showing a step after the step shown in FIG.12;

[0040]FIG. 14 is a partial sectional view showing a second electrodelayer according to another embodiment; and

[0041]FIG. 15 is a partial sectional view showing a second electrodelayer according to a further embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] The present invention will be described below with reference tothe drawings. In each of the drawing, the X direction coincides with thetrack width direction, the Y direction coincides with the direction of aleakage magnetic field from a recording medium, and Z directioncoincides with the movement direction of the recording medium and thelamination direction of layers constituting a giant magnetoresistiveelement.

[0043]FIG. 1 is a schematic sectional view showing the structure of agiant magnetoresistive (GMR) element 1 according to a first embodimentof the present invention, as viewed from a surface facing the recordingmedium. The GMR element 1 is used for, for example, a thin film magnetichead of a hard disk device, for detecting a leakage magnetic field fromthe recording medium by utilizing a GMR effect.

[0044] The GMR element 1 is formed on a lower gap layer 2 comprising aninsulating material such as alumina (Al₂O₃) or the like. The GMR element1 comprises a seed layer 3, a first antiferromagnetic layer 4, a pinnedmagnetic layer 5, a nonmagnetic material layer 6, a free magnetic layer11, a nonmagnetic layer 13, ferromagnetic layers 12, secondantiferromagnetic layers 14 and electrode layers 20, which are laminatedin that order on the lower gap layer 2. The nonmagnetic layer 13, theferromagnetic layers 12 and the second antiferromagnetic layers 14 arelongitudinal bias layers for the free magnetic layer 11. Although notshown in the drawing, an undercoat layer composed of alumina, anunderlying layer composed of Ta, a NiFe alloy or the like, and a lowershield layer composed of a magnetic material such as a NiFe alloy or thelike may be formed below the lower gap layer 2 in that order from analumina-titanium carbide substrate.

[0045] The seed layer 3 is an underlying layer for arranging crystalgrowth of each of the first antiferromagnetic layer 4 and the layerslaminated thereon, and comprises a NiFe alloy, a NiCr alloy, a NiFeCralloy, Cr, or the like. The underlying layer composed of Ta or the likemay be formed between the seed layer 3 and the lower gap layer 2, or theunderlying layer may be formed instead of the seed layer 3.

[0046] The first antiferromagnetic layer 4 produces a great exchangecoupling magnetic field between the pinned magnetic layer 5 and thefirst antiferromagnetic layer 4 by a heat treatment so that themagnetization direction of the pinned magnetic layer 5 is pinned in theY direction shown in the drawing. The first antiferromagnetic layer 4comprises a PtMn alloy, a X—Mn (wherein X is at least one element of Pd,Ir, Rh, Ru, Os, Ni, and Fe) alloy, or a Pt—Mn—X′ (wherein X′ is at leastone element of Pd, Ir, Rh, Ru, Au, Ag, Os, Cr, Ni, Ar, Ne, Xe, and Kr)alloy. Although these alloys have a disordered face-centered cubicstructure (fcc) immediately after deposition, the fcc structure istransformed to a CuAuI-type ordered face-centered tetragonal structure(fct) by a heat treatment. Therefore, when the first antiferromagneticlayer 4 is formed by using any one of the alloys, a great exchangecoupling magnetic field can be produced between the firstantiferromagnetic layer 4 and the pinned magnetic layer 5 by the heattreatment.

[0047] The pinned magnetic layer 5 has a laminated ferrimagnetic pinnedstructure comprising a first pinned magnetic layer 5 a, a nonmagneticintermediate layer 5 b and a second pinned magnetic layer 5 c. In thisstructure, magnetization of the first pinned magnetic layer 5 a ispinned in the height direction by exchange coupling with the firstantiferromagnetic layer 4, and magnetization of the second pinnedmagnetic layer 5 c is pinned in a direction at 180° (antiparallel) withrespect to the magnetization direction of the first pinned magneticlayer 5 a through the nonmagnetic intermediate layer 5 b. With thepinned magnetic layer 5 having the laminated ferrimagnetic pinnedstructure, the magnetization direction of the pinned magnetic layer 5can be stably pinned by a synergy effect of antiparallel couplingbetween the first and second pinned magnetic layers 5 a and 5 c throughthe nonmagnetic intermediate layer 5 b and exchange coupling between thefirst pinned magnetic layer 5 a and the first antiferromagnetic layer 4.Of course, the pinned magnetic layer 5 may have a single layerstructure.

[0048] Each of the first and second pinned magnetic layers 5 a and 5 ccomprises a ferromagnetic material, for example, a NiFe alloy, Co, aCoNiFe alloy, a CoFe alloy, a CoNi alloy, or the like. Particularly,each of the first and second pinned magnetic layers 5 a and 5 cpreferably comprises a CoFe alloy or Co. Also, the first and secondpinned magnetic layers 5 a and 5 c preferably comprises the samematerial. The nonmagnetic intermediate layer 5 b comprises a nonmagneticmaterial, for example, at least one of Ru, Rh, Pd, Ir, Os, Re, Cr, Cu,Pt. and Au. Particularly, the nonmagnetic intermediate layer 5 bpreferably comprises Ru or Cu.

[0049] The nonmagnetic material layer 6 is a layer for preventingmagnetic coupling between the pinned magnetic layer 5 and the freemagnetic layer 11, and a sensing current mainly flows through the layer.The nonmagnetic material layer 6 comprises a nonmagnetic material havingconductivity, such as Cu, Cr, Au, Ag, or the like, and particularlypreferably comprises Cu.

[0050] The free magnetic layer 11 has a central portion (track widthregion) 11 a in which magnetization can be rotated with an externalmagnetic field, and both side portions 11 b provided on both sides ofthe central portion 11 a in the track width direction. The free magneticlayer 11 is formed to have a larger magnetic moment (magnetic thickness)per unit area than that of the ferromagnetic layers 12. The magnitude ofmagnetic moment per unit area can be represented by a product ofsaturation magnetization M_(s) and thickness t.

[0051] The nonmagnetic layer 13 has a central portion 13 a positioned onthe central portion 11 a of the free magnetic layer 11, and both sideportions 13 b positioned on the respective both side portions 11 b ofthe free magnetic layer 11, the ferromagnetic layers 12 being formed onthe both side portions 13 b. Both side portions 13 b of the nonmagneticlayer 13 are formed to a thickness with which RKKY coupling energyproduced between both side portions 11 b of the free magnetic layer 11and the ferromagnetic layers 12 is a first peak or second peak value forantiparallel alignment. Namely, both side portions 11 b of the freemagnetic layer 11 are coupled with the respective ferromagnetic layers12 in antiparallel to each other through both side portions 13 b of thenonmagnetic layer 13 so that the magnetization directions of the freemagnetic layer 11 and each ferromagnetic layer 12 are antiparallel toeach other. The nonmagnetic layer 13 may be composed of at least one ofRu, Rh, Pd, Ir, Os, Re, Cr, Cu, Pt, and Au, and particularly preferablyRu or Cu. Although, in this embodiment, the nonmagnetic layer 13 isformed over the entire surface of the free magnetic layer 11, thenonmagnetic layer 13 may be formed only on both side portions 11 b ofthe free magnetic layer 11.

[0052] Each of the free magnetic layer 11 and the ferromagnetic layers12 comprises a ferromagnetic material, for example, a NiFe alloy, Co, aCoNiFe alloy, a CoFe alloy, a CoNi alloy, or the like. The free magneticlayer 11 and the ferromagnetic layers 12 preferably comprise the samematerial. In the use of the same material, the thickness of each freeferromagnetic layer 12 is made smaller than that of the free magneticlayer 11 so that the magnetic moment per unit area of the free magneticlayer 11 is larger than that of the ferromagnetic layers 12. With thefree magnetic layer 11 and the ferromagnetic layers 12 each having asingle layer structure, the free magnetic layer 11 or the ferromagneticlayers 12, or both of the layers 11 and 12 preferably comprise a CoNiFealloy. On the other hand, with the free magnetic layer 11 and theferromagnetic layers 12 each having a multi-layer structure, the freemagnetic layer 11 preferably comprises a laminate of a NiFe alloy and aCoFe alloy which are laminated in order, and each of the ferromagneticlayers 12 preferably comprises a laminate of a CoFe alloy and a NiFealloy which are laminated in order.

[0053] The second antiferromagnetic layers 14 are formed on therespective ferromagnetic layers 12 to produce exchange coupling magneticfields between the second antiferromagnetic layers 14 and the respectiveferromagnetic layer 12 by a heat treatment, such that the magnetizationdirection of each ferromagnetic layer 12 is pinned in the track widthdirection (the rightward direction in FIG. 1). When magnetization ofeach ferromagnetic layer 12 is pinned, magnetizations of both sidepotions 11 b of the free magnetic layer 11 are pinned in a direction(the leftward direction in FIG. 1; antiparallel) opposite to themagnetization direction of the ferromagnetic layers 12 through both sideportions 13 b of the nonmagnetic layer 13, and the magnetizationdirection of the central portion 11 a between both side portions 11 b isaligned in antiparallel to the ferromagnetic layers 12. In thisembodiment, the track width Tw is regulated by the distance between thesecond antiferromagnetic layers 14 in the track width direction, and thetrack width Tw coincides with the dimension of the central portion 11 aof the free magnetic layer 11 in the track width direction.

[0054] Like the first antiferromagnetic layer 4, each of the secondantiferromagnetic layers 14 comprises a PtMn alloy, a X—Mn (wherein X isat least one element of Pd, Ir, Rh, Ru, Os, Ni, and Fe) alloy, or aPt—Mn—X′ (wherein X′ is at least one element of Pd, Ir, Rh, Ru, Au, Ag,Os, Cr, Ni, Ar, Ne, Xe, and Kr) alloy.

[0055] Each of the electrode layers 20 comprises a first electrode layer21 formed on the first antiferromagnetic layer 4 to make contact withthe end surfaces of the first antiferromagnetic layer 4, the pinnedmagnetic layer 5, the nonmagnetic material layer 6, the free magneticlayer 11 and each second antiferromagnetic layer 12 at each side in thetrack width direction, and a second electrode layer 22 formed on thefirst electrode layer 21 and each second antiferromagnetic layer 14.Each of the first and second electrode layers 21 and 22 comprises aconductive material having low resistivity, for example, Au, Cu, α-Ta,Cr, or the like. The sensing current supplied to the second electrodelayers 22 flows into the nonmagnetic material layer 6, the free magneticlayer 11 and the pinned magnetic layer 5 through the respective firstelectrode layers 21.

[0056] Although not shown in the drawing, an upper shield layer isformed on the second electrode layers 22 and the central portion 13 a ofthe nonmagnetic layer 13 through an upper gap layer composed of, forexample, alumina.

[0057] The above-described GMR element 1 is characterized in that atleast the free magnetic layer 11, the nonmagnetic layer 13 and theferromagnetic layers 12 have continuous end surfaces α at both sides inthe track width direction. In this way, when both ends are thecontinuous surfaces, magnetostatic coupling can be produced between thefree magnetic layer 11 and each ferromagnetic layer 12 at both endsurfaces, and thus a demagnetizing field applied to the free magneticlayer 11 in the track width direction thereof can be weakened by themagnetostatic coupling. Therefore, even when the dimension FW of thefree magnetic layer 11 in the track width direction is decreased bynarrowing the track, disturbance of magnetization at both end surfacesof the free magnetic layer and the ferromagnetic layer 12 anddisturbance of magnetization within the track width region can besuppressed.

[0058] The GMR element 1 is also characterized in that the ratio (FW/FL)of the dimension FW of the free magnetic layer 11 in the track widthdirection to the dimension FL of the ferromagnetic layers 12 in thetrack width direction is 1.1 to 2.0. The dimension FL of theferromagnetic layers 12 in the track width direction is a totaldimension (FL1+FL2) of a pair of the ferromagnetic layers 12 shown inFIG. 1. With the ratio (FW/FL) within the above range, magnetizations ofboth side portions 11 b of the free magnetic layer 11 can beappropriately pinned by antiparallel coupling with the ferromagneticlayers 12, and magnetization rotation in the central portion 11 a of thefree magnetic layer 11 can be facilitated with the external magneticfield. Therefore, a distortion and instability of the reproductionwaveform can be suppressed to improve output sensitivity, and theoccurrence of side reading can be prevented. The magnetization rotationin the central portion 11 a of the free magnetic layer 11 is furtherfacilitated by weakening RKKY antiparallel coupling between both sideportions 11 b of the free magnetic layer 11 and the ferromagnetic layers12, thereby further improving the output sensitivity. The strength ofantiparallel coupling between the ferromagnetic layers 12 and both sideportions 11 b of the free magnetic layer 11 can be controlled bycontrolling the thickness of both side portions 13 b of the nonmagneticlayer 13.

[0059] The GMR element 1 is further characterized in that the electrodelayers 20 are formed in contact with the tops of the respective secondantiferromagnetic layers 14 and the end surfaces of the layers rangingfrom the second antiferromagnetic layers 14 to the pinned magnetic layer5 at both sides in the track width direction, and thus the sensingcurrent is supplied without passing through the second antiferromagneticlayers 14. When the sensing current is supplied without passing throughthe second antiferromagnetic layers 14, the element resistance can bedecreased, as compared with a conventional element in which a sensingcurrent is supplied through the second antiferromagnetic layers 14. As aresult, the occurrence of high-frequency noise can be suppressed toimprove the SN ratio.

[0060] The method of manufacturing the GMR element shown in FIG. 1 willbe described with reference to FIGS. 2 to 8. First, the seed layer 3,the first antiferromagnetic layer 4, the fist pinned magnetic layer 5 a,the nonmagnetic intermediate layer 5 b and the second pinned magneticlayer 5 c constituting the pinned magnetic layer 5, the nonmagneticmaterial layer 6, the free magnetic layer 11, and the nonmagnetic layer13 are continuously deposited on the lower gap layer 2 composed ofalumina (FIG. 2). This continuous deposition step is performed by a thinfilm forming process such as sputtering, evaporation, or the like in asame vacuum deposition apparatus.

[0061] The seed layer 3 comprises a NiFe alloy, a NiCr alloy, a NiFeCralloy, Cr, or the like. The first antiferromagnetic layer 4 comprises aPtMn alloy, a X—Mn (wherein X is at least one element of Pd, Ir, Rh, Ru,Os, Ni, and Fe) alloy, or a Pt—Mn—X′ (wherein X′ is at least one elementof Pd, Ir, Rh, Ru, Au, Ag, Os, Cr, Ni, Ar, Ne, Xe, and Kr) alloy. Withthe first antiferromagnetic layer 4 comprising any one of these alloymaterials, a large exchange coupling magnetic field can be produced inmagnetic field annealing in a subsequent step.

[0062] Each of the first and second pinned magnetic layers 5 a and 5 cmay comprise a magnetic material, for example, a NiFe alloy, Co, aCoNiFe alloy, a CoFe alloy, a CoNi alloy, or the like, and the first andsecond pinned magnetic layers 5 a and 5 b preferably comprise the samematerial. The nonmagnetic intermediate layer 5 b may comprise any one ofRu, Rh, Pd, Ir, Os, Re, Cr, Cu, Pt. and Au, and particularly preferablycomprises Ru or Cu. The pinned magnetic layer 5 may comprise a singleferromagnetic material layer.

[0063] The nonmagnetic material layer 6 may comprise a nonmagneticmaterial having conductivity, for example, Cu, Cr, Au, Ag, or the like.Particularly, the nonmagnetic material layer 6 preferably comprises Cu.The free magnetic layer 11 may comprise any one of a NiFe alloy, Co, aCoFe alloy, a CoNi alloy, and a CoFeNi alloy. The nonmagnetic layer 13may comprise any one of Ru, Rh, Pd, Ir, Os, Re, Cr, Cu, Pt, and Au, andparticularly preferably comprises Ru or Cu. The nonmagnetic layer 13 isdeposited to a thickness larger than that in the completed state shownin FIG. 1.

[0064] After the nonmagnetic layer 13 is deposited, a first heattreatment is performed. Namely, a heat treatment is performed at a firstheat treatment temperature with a first magnetic field applied in adirection (height direction; the Y direction shown in the drawing)perpendicular to the track width direction to produce an exchangecoupling magnetic field between the first antiferromagnetic layer 4 andthe first pinned magnetic layer 5 a, for pinning magnetization of thefirst pinned magnetic layer 5 a in the height direction.

[0065] After the annealing treatment, as shown in FIG. 3, the surface ofthe nonmagnetic layer 13 is cleaned by low-energy ion milling. In thisembodiment, low-energy ion milling is performed by using Ar ionsaccelerated with, for example, 100 to 200 eV. In this step, thenonmagnetic layer 13 is controlled to a thickness with which RKKYcoupling energy produced between the free magnetic layer 11 and theferromagnetic layer 12 through the nonmagnetic layer 13 is a first peakvalue (or second peak value) for antiparallel alignment. For example,when the nonmagnetic layer 13 is composed of Ru, the thickness ispreferably controlled to 6 Å to 12 Å, while when the nonmagnetic layer13 is composed of Cu, the thickness is preferably controlled to 7 Å to12 Å. In FIG. 3, the ion milling direction is shown by arrows H.

[0066] Next, as shown in FIG. 4, the ferromagnetic layer 12 and thesecond antiferromagnetic layer 14 are continuously deposited on thenonmagnetic layer 13 by sputtering or evaporation.

[0067] The ferromagnetic layer 12 preferably comprises the same materialas the free magnetic layer 11. When the free magnetic layer 11 and theferromagnetic layer 12 comprise the same material, the ferromagneticlayer 12 is formed to a smaller thickness than that of the free magneticlayer 11 so that the magnetic moment per unit area of the free magneticlayer 11 is larger than that of the ferromagnetic layer 12. Each of thefree magnetic layer 11 and the ferromagnetic layer 12 may be formed in asingle layer structure or multi-layer structure. With the free magneticlayer 11 and the ferromagnetic layer 12 each having a single layerstructure, at least one of the free magnetic layer 11 and theferromagnetic layer 12 preferably comprises a CoNiFe alloy. On the otherhand, with the free magnetic layer 11 and the ferromagnetic layer 12each having a multi-layer structure, the free magnetic layer 11preferably comprises a laminate of a NiFe alloy and a CoFe alloy whichare laminated in order, and the ferromagnetic layer 12 preferablycomprises a laminate of a CoFe alloy and a NiFe alloy which arelaminated in order.

[0068] Then, a photoresist solution is coated on the secondantiferromagnetic layer 14, and then patterned in the track width regionby exposure and development to form a resist layer R shown in FIG. 5 ata position corresponding to the track width region. The resist layer Ris a lift off resist layer. After the resist layer R is formed, ionmilling is performed until the first antiferromagnetic layer 4 isexposed from both sides of the resist layer R in the track widthdirection (FIG. 5). In FIG. 5, the ion milling direction is shown byarrows H. The ion milling may be continued until the seed layer 3 or thelower gap layer 2 is exposed.

[0069] In the ion milling step, the portions shown by dotted lines inFIG. 5 out of the track width region (portions of the secondantiferromagnetic layer 14, the ferromagnetic layer 12, the nonmagneticlayer 13, the free magnetic layer 11, the nonmagnetic material layer 6,the pinned magnetic layer 5 and the first antiferromagnetic layer 4) areremoved. As a result, the dimension FW of the free magnetic layer 11 inthe track width direction is regulated, and the layers ranging from thesecond antiferromagnetic layer 14 to the first antiferromagnetic layer 4have the continuous end surfaces α at both sides in the track widthdirection. When the continuous end surfaces α are formed, magnetostaticcoupling can be produced between the free magnetic layer 11 and theferromagnetic layer 12 at both end surfaces 11 c and 12 c of the freemagnetic layer 11 and the ferromagnetic layer 12, and thus the influenceof a demagnetizing field in both side portions of the free magneticlayer 11 and the ferromagnetic layer 12 can be decreased by themagnetostatic coupling.

[0070] Then, as shown in FIG. 6, the first electrode layers 21 areformed on the first antiferromagnetic layer 4 to make contact with theend surfaces of the layers ranging from the second antiferromagneticlayer 14 to the first antiferromagnetic layer 4 at both sides in thetrack width direction. Each of the first electrode layers 21 maycomprise a conductive material having low resistivity, for example, Au,Cu, α-Ta, Cr, or the like.

[0071] After the first electrode layers 21, the resist layer R isremoved by liftoff, and the second electrode layers 22 are formed on thefirst electrode layers 21 and regions of the second antiferromagneticlayer 14 out of the track width region, as shown in FIG. 7. Namely, asecond electrode layer 22 and metal mask layer 23 are formed on thefirst electrode layers 21 and the second antiferromagnetic layer 14, andthen the metal mask layer 23 and the second electrode layer 22 areremoved from the track width region by reactive ion etching. The secondelectrode layers 22 preferably comprise the same conductive material asthat of the first electrode layers 21. The second electrode layers 22can be formed by a liftoff method. In the liftoff method, the metal masklayers 23 need not be formed.

[0072] When the sensing current is supplied to the second electrodelayers 22, the sensing current flows into the nonmagnetic material layer6, the pinned magnetic layer 5 and the free magnetic layer 11 throughthe first electrode layers 21 having low resistivity. Namely, thesensing current can be supplied without passing through the secondantiferromagnetic layer 14 having extremely higher resistivity than theelectrode layers 20. Therefore, the element resistance of the GMRelement 1 to be formed can be sufficiently suppressed to avoid adecrease in the SN ratio due to high-frequency noise.

[0073] After the second electrode layers 22 are formed, as shown in FIG.8, reactive ion etching (RIE) treatment is performed by using the metalmask layers 23 and the second electrode layers 22 as masks to remove thesecond antiferromagnetic layer 14, the ferromagnetic layer 12 and thenonmagnetic layer 13 from the track width region. In this embodiment,the reactive ion etching is stopped when the thickness of thenonmagnetic layer 13 (central portion 13 a) in the track width regionbecomes 3 Å or less. The nonmagnetic layer 13 may be completely removedfrom the track width region, and ion milling may be performed in placeof the reactive ion etching.

[0074] In the reactive ion etching step, the portions shown by dottedlines in FIG. 8 are moved to form a recess β. Namely, the ferromagneticlayer 12 and the second antiferromagnetic layer 14 are present only onboth side portions 11 b of the free magnetic layer 11. Therefore, thetrack width Tw is regulated by the distance between the secondantiferromagnetic layers 14 in the track width direction, and thedimension FL of the ferromagnetic layers 12 in the tack width directionis regulated.

[0075] In this embodiment, the ratio (FW/FL) of the dimension FW of thefree magnetic layer 11 in the tack width direction to the dimension FLof the ferromagnetic layers 12 in the track width direction is set to1.1 to 2.0 so as to appropriately pin magnetization of each side portion11 b of the free magnetic layer 11 and facilitate magnetization rotationof the central portion 11 a with the external magnetic field.

[0076] Then, a second heat treatment is performed. In this step, a heattreatment is performed at a second heat treatment temperature lower thanthe blocking temperature of the first antiferromagnetic layer 4 with asecond magnetic field applied in a direction (track width direction)perpendicular to the first magnetic field, the second magnetic fieldbeing higher than the coercive force of the free magnetic layer 11 andthe ferromagnetic layer 12 and lower than the flip flop magnetic field.In this heat treatment, an exchange coupling magnetic field is producedbetween the ferromagnetic layers 12 and the second antiferromagneticlayers 14 to pin the magnetization directions of the ferromagneticlayers 12 in a direction perpendicular to the magnetization direction ofthe pinned magnetic layer 5. The second heat treatment may be performedimmediately after the step shown in FIG. 4. The GMR element shown inFIG. 1 is obtained by the above-described steps.

[0077]FIG. 9 is a partial sectional view showing the structure of a GMRelement 100 according to a second embodiment of the present invention,as viewed from a surface facing a recording medium. The secondembodiment is different from the first embodiment in that each of thesecond antiferromagnetic layers 14 comprises a lower antiferromagneticlayer 14 a and an upper antiferromagnetic layer 14 b. In FIG. 9,substantially the same components as in the first embodiment are denotedby the same reference numerals.

[0078] A nonmagnetic protective layer 15 may be interposed between thelower antiferromagnetic layer 14 a and the upper antiferromagnetic layer14 b. The nonmagnetic protective layer 15 is provided as anantioxidation layer for preventing oxidation of the lowerantiferromagnetic layer 14 a in the manufacturing process, and is formedto a thickness of 3 Å or less. The constituent elements of thenonmagnetic protective layer 5 may diffuse into the lowerantiferromagnetic layer 14 a and/or upper antiferromagnetic layer 14 bin a heat treatment for producing the exchange coupling magnetic fieldbetween the ferromagnetic layer 12 and the lower antiferromagnetic layer14 a, and may be mixed in the lower antiferromagnetic layer 14 a and/orupper antiferromagnetic layer 14 b.

[0079] The upper antiferromagnetic layer 14 b is coupled with the lowerantiferromagnetic layer 14 a through the nonmagnetic protective layer 15to function integrally with the lower antiferromagnetic layer 14 a. Thelower antiferromagnetic layer 14 a is preferably formed to a thicknessof 20 Å to 50 Å so as not to assume the antiferromagnetic properties inthe stage in which only the lower antiferromagnetic layer 14 a isdeposited. Also, the total thickness of the lower antiferromagneticlayer 14 and the upper antiferromagnetic layer 14 b is preferably 80 Åto 300 Å so as to produce a large exchange coupling magnetic fieldbetween the ferromagnetic layer 12 and the lower antiferromagnetic layer14 a by a heat treatment.

[0080] The lower antiferromagnetic layer 14 a and the upperantiferromagnetic layer 14 b preferably comprise the same material suchas a PtMn alloy, a X—Mn (wherein X is at least one element of Pd, Ir,Rh, Ru, Os, Ni, and Fe) alloy, or a Pt—Mn—X′ (wherein X′ is at least oneelement of Pd, Ir, Rh, Ru, Au, Ag, Os, Cr, Ni, Ar, Ne, Xe, and Kr)alloy. On the other hand, the nonmagnetic protective layer 15 maycomprise at least one of Ru, Rh, Pd, Ir, Os, Re, Cr, Cu, Pt, and Au, andparticularly preferably comprises Ru or Cr. In the combination of thematerial for the lower antiferromagnetic layer 14 a and the upperantiferromagnetic layer 14 b and the material for the nonmagneticprotective layer 15, the lower and upper antiferromagnetic layers 14 aand 14 b integrally function to produce a large exchange couplingmagnetic field between the ferromagnetic layer 12 and theseantiferromagnetic layers 14 a and/or 14 b even when the constituentelements of the nonmagnetic protective layer 15 diffuse into the lowerantiferromagnetic layer 14 a and/or the upper antiferromagnetic layer 14b to increase the concentration of the elements of the nonmagneticprotective layer 15 near the interface between the lowerantiferromagnetic layer 14 a and/or the upper antiferromagnetic layer 14b.

[0081] The method of manufacturing the GMR element 100 shown in FIG. 9will be described below with reference to FIGS. 10 to 13. First, theseed layer 3, the first antiferromagnetic layer 4, the first pinnedmagnetic layer 5 a, the nonmagnetic intermediate layer 5 b and thesecond pinned magnetic layer 5 c constituting the pinned magnetic layer5, the nonmagnetic material layer 6, the free magnetic layer 11, thenonmagnetic layer 13, the ferromagnetic layer 12, the lowerantiferromagnetic layer 14 a and the nonmagnetic protective layer 15 arecontinuously deposited on the lower gap layer 2 composed of alumina(FIG. 10). This continuous deposition step is performed by a thin filmforming process such as sputtering, evaporation, or the like in a samevacuum deposition apparatus.

[0082] Since the materials and thicknesses of the seed layer 3, thefirst antiferromagnetic layer 4, the first pinned magnetic layer 5 a,the nonmagnetic intermediate layer 5 b, the second pinned magnetic layer5 c, the nonmagnetic material layer 6, the free magnetic layer 11, thenonmagnetic layer 13 and the ferromagnetic layer 12 are the same asthose in the first embodiment, the description of these layers isomitted.

[0083] Like the first antiferromagnetic layer 4, the lowerantiferromagnetic layer 14 a comprise a PtMn alloy, a X—Mn (wherein X isat least one element of Pd, Ir, Rh, Ru, Os, Ni, and Fe) alloy, or aPt—Mn—X′ (wherein X′ is at least one element of Pd, Ir, Rh, Ru, Au, Ag,Os, Cr, Ni, Ar, Ne, Xe, and Kr) alloy. The lower antiferromagnetic layer14 a is preferably formed to a thickness of 20 Å to 50 Å. With athickness in this range, in a stage in which only the lowerantiferromagnetic layer 14 a is formed on the ferromagnetic layer 12, aheat treatment produces no (or a weak) exchange coupling magnetic fieldoccurs between the ferromagnetic layer 12 and the lowerantiferromagnetic layer 14 a.

[0084] The nonmagnetic protective layer 15 is provided as a protectivelayer (antioxidation layer) for preventing oxidation of the lowerantiferromagnetic layer 14 a, and is preferably formed to a thickness of3 Å to 10 Å. The nonmagnetic protective layer 15 may comprise at leastone of Ru, Rh, Pd, Ir, Os, Re, Cr, Cu, Pt, and Au, and particularlypreferably comprises Ru or Cr.

[0085] After the nonmagnetic protective layer 15 is formed, a first heattreatment is performed. Namely, a heat treatment is performed at a firstheat treatment temperature with a first magnetic field applied in adirection (height direction; the Y direction shown in the drawing)perpendicular to the track width Tw to produce an exchange couplingmagnetic field between the first antiferromagnetic layer 4 and the firstpinned magnetic layer 5 a, for pinning magnetization of the first pinnedmagnetic layer 5 a. In this step, the lower antiferromagnetic layer 14 ais less ordered by the first heat treatment because it has a smallthickness so as not to assume the antiferromagnetic properties, asdescribed above, thereby producing no (or a weak) exchange couplingmagnetic field between the lower antiferromagnetic layer 14 a and theferromagnetic layer 12.

[0086] Then, as shown in FIG. 11, the surface of the nonmagneticprotective layer 15 is cleaned by low-energy ion milling. In this step,the nonmagnetic protective layer 15 is controlled to a thickness of 3 Åor less.

[0087] Next, as shown in FIG. 12, the upper antiferromagnetic layer 14 bis formed on the lower antiferromagnetic layer 14 a with the nonmagneticprotective layer 15 provided therebetween. The upper antiferromagneticlayer 14 b is preferably formed so that the total thickness of the upperantiferromagnetic and lower antiferromagnetic layers 14 b and 14 a is 80Å to 300 Å. With a total thickness in this range, the lowerantiferromagnetic layer 14 a and upper antiferromagnetic layer 14 b canintegrally function as the second antiferromagnetic layer 14 to producea large exchange coupling magnetic field between the lowerantiferromagnetic layer 14 a and the ferromagnetic layer 12 by the heattreatment. When the nonmagnetic protective layer 15 is completelyremoved by the low-energy ion milling step shown in FIG. 11, the upperantiferromagnetic layer 14 b is formed directly on the lowerantiferromagnetic layer 14 a.

[0088] After the upper antiferromagnetic layer 14 b is formed, as shownin FIG. 13, a photoresist layer R is formed on the upperantiferromagnetic layer 14 b, and then ion milling is performed untilthe first antiferromagnetic layer 14 is exposed from both sides of theresist layer R in the track width direction (FIG. 13). In FIG. 13, theion milling direction is shown by arrows H. In the ion milling step,portions of each layer shown by dotted lines in FIG. 13 out of the trackwidth region are removed. As a result, the dimension FW of the freemagnetic layer 11 in the track width direction is regulated, and thelayers ranging from the upper antiferromagnetic layer 14 b to the firstantiferromagnetic layer 4 have the continuous end surfaces a at bothsides in the track width direction, thereby producing magnetostaticcoupling between the free magnetic layer 11 and the ferromagnetic layer12 at both side end surfaces 11 c and 12 c. The ion milling may beperformed until the seed layer 3 or the lower gap layer 2 is exposed.

[0089] Then, the first and second electrode layers 21 and 22 are formed,and then the upper antiferromagnetic layer 14 b, the nonmagneticprotective layer 15, the lower antiferromagnetic layer 14 a, theferromagnetic layer 12 and the nonmagnetic layer 13 are removed from thetrack width region by the same steps as those (FIGS. 6 to 8) in thefirst embodiment. As a result, the track width Tw is regulated by thedistance between the upper antiferromagnetic layers 14 b, thenonmagnetic protective layers 15 and the lower antiferromagnetic layers14 a, and the dimension FL of the ferromagnetic layers 12 in the tackwidth direction is regulated.

[0090] Then, a second heat treatment is performed. In this step, a heattreatment is performed at a second heat treatment temperature lower thanthe blocking temperature of the first antiferromagnetic layer 4 with asecond magnetic field applied in a direction (track width direction)perpendicular to the first magnetic field. In this heat treatment, theconstituent element of the nonmagnetic protective layer 15 may diffuseinto the lower antiferromagnetic layer 14 a and/or upperantiferromagnetic layer 14 b, and may be mixed in the lowerantiferromagnetic layer 14 a and/or upper antiferromagnetic layer 14 b.This second heat treatment may be performed immediately after the stepshown in FIG. 12. The GMR 100 shown in FIG. 9 is obtained by theabove-described steps.

[0091] Although, in each of the above embodiments, the electrode layer20 comprises the first and second electrode layers 21 and 22, theelectrode layer 20 may have a single layer structure. Namely, only thefirst electrode layer 21 or the second electrode layer 22 may be formed.When only the second electrode layer 22 is formed, the resist layer R isremoved after the continuous end surfaces a are formed in the step shownin FIG. 5 or 13, and then the second electrode layer 22 is formed onregions of the second antiferromagnetic layer 14 out of the track widthregion and on the continuous end surfaces α, as shown in FIG. 14. In anyone of the cases, the sensing current can be supplied without passingthrough the second antiferromagnetic layers 14 to sufficiently suppressthe element resistance. The electrode layer 20 (second electrode layer22) may be formed to have ends overlaid on the free magnetic layer 11.In this overlaid structure, the element resistance can be furtherdecreased, and the occurrence of side reading can be sufficientlyprevented.

[0092] Although, in each of the above embodiments, the thickness of bothside portions 13 b of the nonmagnetic layer 13 is controlled toappropriately decrease antiparallel coupling between the free magneticlayer 11 and the ferromagnetic layer 12, thereby facilitating rotationin the central portion 11 a of the free magnetic layer 11 and improvingthe output sensitivity. Since magnetostatic coupling occurs between thefree magnetic layer 11 and the ferromagnetic layer 12 at both endsurfaces in the track width direction, the occurrence of side readingcan be sufficiently prevented even when antiparallel coupling betweenthe free magnetic layer 11 and the ferromagnetic layer 12 is weakened.

[0093] The above-described GMR element (100) of the present inventioncan be applied not only to a reproducing thin film magnetic head butalso to a recording/reproducing thin film magnetic head comprising thereproducing thin film magnetic head and a recording inductive headlaminated thereon. The GMR element can also be used as any one ofvarious magnetic sensors.

[0094] In the present invention, at least a free magnetic layer, a nonmagnetic layer and a ferromagnetic layer are formed to have continuousend surfaces at both sides in the tack width direction, and thusmagnetostatic coupling occurs between the free magnetic layer and theferromagnetic layer at both end surfaces. Therefore, the influence of ademagnetizing field applied to the free magnetic layer and theferromagnetic layer can be decreased by the magnetostatic coupling.Thus, even when the dimension of the free magnetic layer in the trackwidth direction is decreased for realizing a narrower track, adisturbance of magnetization within the track width region can besuppressed to improve output sensitivity. Also, in the presentinvention, the ratio (FW/FL) of the dimension of the free magnetic layerto the dimension of the ferromagnetic layer in the track width directionis regulated to 1.1 to 2.0, and thus the output sensitivity can beimproved while sufficiently suppressing a distortion and instability ofa reproduction waveform. Furthermore, in the present invention, thesensing current is supplied without passing through a secondantiferromagnetic layer having high resistivity, and thus the elementresistance can be sufficiently decreased, thereby suppressinghigh-frequency noise and improving the SN ratio.

What is claimed is:
 1. A giant magnetoresistive element comprising: afirst antiferromagnetic layer; a pinned magnetic layer formed on thefirst antiferromagnetic layer so that the magnetization direction ispinned by an exchange coupling magnetic field with the firstantiferromagnetic layer; a nonmagnetic material layer formed on thepinned magnetic layer; a free magnetic layer formed on the nonmagneticmaterial layer so that the magnetization direction of a central portionchanges with an external magnetic field; nonmagnetic layers formed onboth side portions of the free magnetic layer in the track widthdirection; ferromagnetic layers formed on the respective nonmagneticlayers; and second antiferromagnetic layers formed on the respectiveferromagnetic layers to align the magnetization direction of eachferromagnetic layer in a direction perpendicular to the magnetizationdirection of the pinned magnetic layer; wherein at least the freemagnetic layer, the nonmagnetic layers and the ferromagnetic layers havecontinuous end surfaces at both sides in the track width direction.
 2. Agiant magnetoresistive element according to claim 1, wherein the ratio(FW/FL) of the dimension FW of the free magnetic layer to the dimensionFL of the ferromagnetic layers in the track width direction is 1.1 to2.0.
 3. A giant magnetoresistive element according to claim 1, furthercomprising electrode layers formed in contact with the upper surfaces ofthe respective second antiferromagnetic layers and contact with the endsurfaces of the layers ranging from the antiferromagnetic layers to thepinned magnetic layer at both sides in the track width direction.
 4. Agiant magnetoresistive element according to claim 1, wherein each of theelectrode layers comprises a first electrode layer formed in contactwith the end surfaces of the layers ranging from the pinned magneticlayer to each second antiferromagnetic layer at each side in the trackwidth direction, and a second electrode layer formed on the firstelectrode layer and each second antiferromagnetic layer.
 5. A giantmagnetoresistive element according to claim 1, wherein each of thesecond antiferromagnetic layers comprises a lower antiferromagneticlayer laminated on each ferromagnetic layer, and an upperantiferromagnetic layer, each of the lower antiferromagnetic layershaving a thickness of 20 Å to 50 Å.
 6. A giant magnetoresistive elementaccording to claim 5, wherein the total thickness of each lowerantiferromagnetic layer and upper antiferromagnetic layer is 80 Å to 300Å.
 7. A giant magnetoresistive element according to claim 5, furthercomprising nonmagnetic protective layers interposed between the lowerantiferromagnetic and upper antiferromagnetic layers, each of thenonmagnetic protective layers having a thickness of 3 Å or less.
 8. Agiant magnetoresistive element according to claim 7, wherein aconstituent element of the nonmagnetic protective layers is mixed in theupper or lower antiferromagnetic layers.
 9. A giant magnetoresistiveelement according to claim 7, wherein the constituent element of thenonmagnetic protective layers is at least one of Ru, Rh, Pd. Ir, Os, Re,Cr, Cu, Pt, and Au.
 10. A giant magnetoresistive element according toclaim 1, wherein each of the free magnetic layer and the ferromagneticlayers comprises any one of a NiFe alloy, Co, a CoFe alloy, a CoNialloy, and a CoFeNi alloy.
 11. A giant magnetoresistive elementaccording to claim 1, wherein the free magnetic layer and ferromagneticlayers are made of the same magnetic material, and the thickness of theferromagnetic layers is smaller than that of the free magnetic layer.12. A giant magnetoresistive element according to claim 1, wherein eachof the free magnetic layer and ferromagnetic layers comprises a singlelayer, and the free magnetic layer or ferromagnetic layers, or both thefree magnetic layer and ferromagnetic layers comprise a CoFeNi alloy.13. A giant magnetoresistive element according to claim 1, wherein thefree magnetic layer comprises a laminate of a NiFe alloy layer and aCoFe alloy layer, and each of the ferromagnetic layers comprises alaminate of a CoFe alloy layer and a NiFe alloy layer.
 14. A giantmagnetoresistive element according to claim 1, wherein each of thenonmagnetic layers is composed of at least one of Ru, Rh, Pd, Ir, Os,Re, Cr, Cu, Pt, and Au.
 15. A giant magnetoresistive element accordingto claim 1, wherein each of the first antiferromagnetic and/or secondantiferromagnetic layers comprises a PtMn alloy, a X—Mn (wherein X is atleast one element of Pd, Ir, Rh, Ru, Os, Ni, and Fe) alloy, or aPt—Mn—X′ (wherein X′ is at least one element of Pd, Ir, Rh, Ru, Au, Ag,Os, Cr, Ni, Ar, Ne, Xe, and Kr) alloy.